WO2020128029A1

WO2020128029A1 - System for controlling a voltage converter

Info

Publication number: WO2020128029A1
Application number: PCT/EP2019/086775
Authority: WO
Inventors: Mathieu Bertrand; Yann LECOCQ; Hicham LAHBIL
Original assignee: Valeo Equipements Electriques Moteur
Priority date: 2018-12-20
Filing date: 2019-12-20
Publication date: 2020-06-25
Also published as: CN113243080A; JP2022515397A; US11594995B2; EP3900175B1; JP7206392B2; FR3091052B1; EP3900175A1; US20220069758A1; FR3091052A1

Abstract

The invention relates to a system (1) for controlling a voltage converter comprising a plurality of top side switches forming a top set and a plurality of bottom side switches forming a bottom set, the control system (1) comprising: - a module (10) for measuring a voltage V of the direct voltage source B; - a module (11) for comparing the measured voltage V with a first safety threshold OV1; - a control module (12) for controlling the closure of a first set of switches selected from the top set or the bottom set, if the comparison module (11) indicates that the measured voltage V is above the first safety threshold OV1.

Description

Title of the invention Control system of a voltage converter

[1] [The present invention relates to electrical systems comprising a rotary electrical machine for a motor vehicle controlled by a voltage converter. More specifically, it relates to a control system for a voltage converter and an electrical system comprising a rotating electrical machine and such a control system.

[2] There are known voltage converters comprising a system of

control and a plurality of switching arms mounted in parallel, each arm comprising a high side switch and a low side switch connected to each other at a midpoint, each midpoint being intended to be connected to at least a phase of a rotating electric machine. The control system controls the opening or closing of each switch to control the power to the electric machine. The low-side switches or the high-side switches are electronic power switches, for example of the metal-oxide field effect transistor type, also known by the acronym MOSFET from English (Metal Oxide Semiconductor Field Effect Transistor). The switches allow the phases of a stator to be supplied, either in an engine mode from a battery electrically supplying an on-board vehicle network, or in an alternator mode to supply the on-board network and recharge a vehicle battery. . In the case of an electronic machine comprising three phases to the stator, the voltage converter comprises three switches on the low sides each connected to one of the three phases and to ground and three switches on the high side each connected to one of the three phases and to a terminal positive corresponding to the on-board network of the motor vehicle.

[3] Following a failure of electrical equipment in the motor vehicle connected to the on-board network, an overvoltage on the on-board network may occur, that is to say the appearance of a voltage on the network on board much higher than the nominal voltage of this network. [4] For example, such an overvoltage can occur in the event of a malfunction of a switch of the voltage converter which remains in the open state or which remains in the closed state while the control system commands respectively in closed or open state.

[5] Such an overvoltage can damage or reduce the reliability not only of the rotating electrical machine or the voltage converter and its control system, but also of any electrical devices connected to the on-board network.

[6] To limit or stop the overvoltage, it is known that the control system of the electric machine includes detection devices associated with each of the switches. Such a detection device makes it possible to detect and identify a fault of the switch with which it is associated and to control the closing and the opening of the other switches according to the fault identified to limit or stop the overvoltage.

[7] For example, in the case of a high side switch which remains in a closed state, the fault detector of this switch will detect a state fault remained closed for this switch and transmit the detection information of this defect in a control module of the control system which will command the closing of the two other high switches and thus put the rotating electric machine in safety by setting all the phases of the stator to the same potential (ie the phases are in short circuit).

[8] However, such a control system must include as many fault detectors as there are switches, which generates significant cost and difficulties in accommodating these fault detectors within the control system.

[9] SUMMARY OF THE INVENTION

[10] The invention aims to at least partially overcome these drawbacks.

[11] To this end, the invention relates to a system for controlling a voltage converter, the voltage converter being intended to connect a rotary electrical machine to a DC voltage source, in particular to an on-board network, the converter voltage comprising a plurality of switching arms mounted in parallel, each arm comprising a switch high side and a low side switch connected to each other at a midpoint intended to be connected to said rotary electrical machine, the high side switches forming a high group and the low side switches forming a low group, the control system comprising:

1. a module for measuring a voltage of the DC voltage source,

2. a module for comparing the voltage measured with a first threshold of

security,

3. a control module for generating a command to close a first group of switches, chosen from the high group or the low group, if the comparison module indicates that the measured voltage is greater than the first safety threshold.

[12] By high side or low side switch means a switch

power supply electronics, for example of the IGBT transistor type (from the English Insulated Gâte Bipolar Transistor) or of the metal-oxide field effect transistor type, also known by the acronym MOSFET from the English (Metal Oxide Semiconductor Field Effect Transistor).

[13] Thus, the control system protects the voltage converter and the

rotating electrical machine by systematically closing all the switches on the same side when an overvoltage is detected.

[14] Such a system, by its systematic side, does not require the installation of fault detection and identification means at the level of each switch. It is therefore less bulky and less expensive to implement than the previous control systems.

[15] In the case where the control system commands all the switches of the low group to close when the measured voltage is above the first safety threshold, the voltage converter is thus protected when one of the high side switches switches to open circuit (the switch remains open regardless of the command it receives) or when one of the low-side switches short-circuits (the switch remains closed regardless of the command it receives) . [16] In the case where the control system commands all the switches of the high group to close when the measured voltage is above the first safety threshold, the voltage converter is thus protected when one of the high side switches short-circuited or when one of the low-side switches goes into open circuit.

[17] In both cases, the voltage converter is also protected against an overvoltage on the on-board network created by equipment other than the voltage converter and / or the rotating electrical machine.

[18] The device according to the invention may also have one or more of the characteristics below, considered individually or in all technically possible combinations:

[19] According to a particular embodiment of the invention, when the voltage

measured is greater than or equal to the first safety threshold, the control module is also designed to generate a command to open switches other than those of the first group.

[20] This avoids a short circuit and damages the switches of the

voltage converter if one of the switches in the first group has failed.

[21] According to one embodiment, the voltage measured is the voltage of the DC voltage source. For example, the measurement module measures the voltage between two terminals of the voltage converter intended to be connected to the DC voltage source.

[22] According to one embodiment, the first safety threshold is between 1.10 and 1.25 times the nominal voltage of the DC voltage source

converter power supply, for example 1.2 times the nominal voltage of the DC voltage source. For example, the nominal supply voltage is forty-eight volts, and the first safety threshold is between fifty-three volts and sixty volts.

[23] According to one embodiment, the comparison module compares the measured supply voltage to a second safety threshold higher than the first safety threshold and the control module is further designed for, when the measured voltage is higher or equal to the second safety threshold, generate a command to close a second group of switches selected from the group of high side switches or the group of low side switches, said second group of switches being different from said first group of switches.

[24] Such a control system makes it possible to put the voltage converter in safety as soon as one of the switches of the voltage converter is in short-circuit or in open circuit.

[25] In a variant of this embodiment, the control system is configured not to command the closing of the second group

switches before the first group of switches has been closed.

[26] In a particular embodiment of the invention, the second safety threshold is between 1.2 and 1.4 times the nominal voltage of the DC voltage source of the voltage converter, for example 1.33 times the nominal voltage of the source of continuous voltage.

[27] Thus, we remain in voltage values which do not cause deterioration of the components of the voltage converter.

[28] In an exemplary implementation of this embodiment, the nominal voltage of the DC voltage source is equal to forty-eight volts and the second safety threshold is between fifty-eight and sixty-seven volts, for example sixty-four volts.

[29] In another embodiment of the invention, the second threshold of

safety is equal to the sum of the first safety threshold and at least one voltage between four volts and twelve volts.

[30] In another embodiment of the invention, the control module is further designed to generate an opening command for the first group of switches, when the measured voltage is greater than or equal to the second safety threshold.

[31] This avoids a short circuit and damages the switches of the

voltage converter.

[32] In another embodiment of the invention, the switches of the first group remain closed, when the measured voltage is greater than or equal to the second security threshold. This makes it possible to cause a short circuit and to use either the vehicle's short circuit protection device, for example a fast-blow fuse, or to use one of the switches on each arm, damaging them until let them all be open.

[33] According to one embodiment, the first group of switches is the group of low side switches.

[34] According to one embodiment, the first group of switches is the group of high side switches.

[35] The invention also relates to a control unit for controlling the high side and low side switches, said control unit comprising a previously described control system which may include characteristics of one or more of the embodiments described previously.

[36] The invention also relates to an electrical system comprising:

at. first and second power supply terminals intended to be connected to a DC voltage source, in particular to a battery of a motor vehicle,

b. a rotary electrical machine comprising a stator having at

minus three phases,

vs. a voltage converter to supply the electric machine

rotating from said DC voltage source, the voltage converter comprising:

i. a plurality of switching arms mounted in parallel, each arm comprising a high side switch and a low side switch connected to each other at a midpoint, each midpoint being connected to at least one phase of said machine electric rotating, and

ii. a control unit for the high side and low side switches, said control unit comprising a control system according to the invention.

[37] The electrical system has the same advantages, mentioned above, as the control system. [38] In a particular embodiment of the electrical system, the control unit further comprises at least one fault detection module, for example a phase current direction fault module, and in which when the fault module detects a fault, the control unit orders the first group of switches to close.

[39] In a particular embodiment of the electrical system, the unit

order also includes:

• a controller designed to control the high side and low side switches,

• a machine control module intended to receive a unit of

electronic control of the vehicle a setpoint for either putting the rotary electric machine in engine mode, or putting the rotary electric machine in alternator mode, and arranged to transform this setpoint into a command for controlling the switches on the high side and on the low side of the converter voltage,

• a logic module to prioritize commands issued by the control system over commands issued by the machine control module, the logic module transmitting to the controller the switch command received either by the machine control module or by the control system .

[40] The use of a logic module makes it possible to ensure that the controller receives a single command and thus to avoid a malfunction of the electrical system.

[41] The invention also relates to a method for controlling a system of

control of a voltage converter according to the invention, the voltage converter being connected to a rotating electrical machine and to a DC voltage source, in particular to an on-board network of a motor vehicle, said method comprising:

1. a step of measurement by the module for measuring the voltage of the DC voltage source,

2. a step of comparison by the module for comparing the voltage measured with a first safety threshold, and 3. a step of generating by the control module a command to close a first group of switches chosen from the high group or the low group, if the measured voltage is greater than the first safety threshold.

[42] The invention also relates to a method for securing a system

electric comprising an electric machine comprising a stator having at least three phases, a voltage converter for supplying the rotating electric machine from a direct voltage source, the voltage converter comprising:

1. a plurality of switching arms mounted in parallel, each arm

comprising a high side switch connected to a positive terminal of the DC voltage source and a low side switch connected to the vehicle ground or to a negative terminal of the DC voltage source, the low switch and the high switch of each arm being connected to each other at a midpoint, each midpoint being connected to at least one phase of said rotary electrical machine, and,

2. a control unit comprising a control system according to

the invention with or without the characteristics of the various embodiments,

[43] the method for securing an electrical system comprises the steps:

1. for measuring a voltage from the DC voltage source,

2. comparing the voltage measured with a first safety threshold,

3. for closing a first group of switch switches, chosen from the group of high side switches or the group of low side switches, when the measured supply voltage is greater than the first safety threshold.

[44] Brief description of the drawings:

[45] Other characteristics and advantages of the invention will emerge clearly from the description which is given below thereof, by way of indication and in no way limiting, with reference to the appended figures, among which: [46] [Fig 1] shows a block diagram of an electrical system comprising a control unit comprising a control system according to an example of a first embodiment.

[47] [Fig 2] shows a block diagram of a control unit

comprising a control system according to an example of the first embodiment.

[48] [Fig 3] and [Fig 4] represent a histogram representing the voltage measured across a DC voltage source.

[49] For clarity, identical or similar elements are identified by identical reference signs in all of the figures.

[50] Detailed description

[51] [Fig.1] shows a block diagram of an SE electrical system

comprising a first power supply terminal B + and a second power supply terminal B- connected to a DC power source B in this case a 48 V DC power source, for example a battery of a motor vehicle enabling other electrical equipment not shown in the vehicle to be supplied via an on-board network. The DC voltage source may include the battery of a motor vehicle and a block of capacitors mounted in parallel with the battery of the vehicle. In this example, the second terminal B- is the earth of the electrical system SE.

[52] The electrical system SE comprises a rotating electrical machine M

comprising a stator having at least three phases U, V, W and three coils u, v, w wound in the stator. In this example, the coils u, v, w are mounted in a star and each comprise at their output the corresponding phase U, V, W respectively.

[53] The electrical system SE further comprises a voltage converter O for supplying the rotating electrical machine M from said DC voltage source B.

[54] The voltage converter O comprises a plurality of arms of

switching connected in parallel between terminals B + and B-. The voltage converter O comprises as many arms as the rotary electric machine M has phases. In this case, in the example described here, the voltage converter O comprises three arms. Thus, the voltage converter O comprises a first arm X, a second arm Y and a third arm Z.

[55] Each arm X, Y, Z includes a high side switch HS_X, HS_Y, HS_Z and a low side switch LS_X, LS_Y, LS_Z. Each switch on the top and bottom side of an arm X, Y, Z are connected to each other at a midpoint PX, PY, PZ. The high side switches form a switch group, called the HS high group. Likewise, the low side switches form a switch group, called the BS low group.

[56] In the example described here, each high side or bottom side switch is a metal-oxide field effect transistor each comprising a freewheeling diode.

[57] In this case, in this example, there is therefore on the first arm X a

first high side switch HS_X connected to a first low side switch LS_X by a first midpoint PX, on the second arm Y a second high side switch HS_Y connected to a second low side switch LS_Y by a second midpoint PY and a third high side switch HS_Z, respectively connected to a third low side switch LS_Z by a third midpoint PZ.

[58] Each midpoint PX, PY, PZ is connected to at least one phase U, V, W of said rotary electrical machine M, in this case in this example the first midpoint PX at phase U, the second midpoint PY in phase V and the third midpoint Z in phase W.

[59] The voltage converter O further comprises a control unit U for the high side switches HS_X, HS_Y, HS_Z and the low side switches LS_X, LS_Y, LS_Z. Said control unit U therefore comprises for each switch an output connected to the control of the corresponding switch. In order not to overload Figure 1, only the connection between an output of the control unit U and the control of the third low side switch LS_Z and another output of the control unit U and the control of the second side switch top HS_Y were represented. [60] The control unit U controls the switches of each arm X, Y, Z in PWM pulse width modulation, better known by the acronym

"PWM" from English "Puise Width Modulation".

[61] [Fig 2] shows a block diagram of the control unit U.

[62] The control unit U comprises a control system 1 comprising a module 10 for measuring a voltage of the DC voltage source B. In the example described here, the measurement module 10 measures a voltage V aux terminals B + and B-. In other words, in the example described here, the voltage module 10 measures the voltage of the DC voltage source B having a nominal voltage of 48 Volts.

[63] The control system 1 further comprises a comparison module 11 arranged to receive from the measurement module 10 the measured voltage V. The comparison module 11 compares the measured voltage V to a first safety threshold OV1. The first safety threshold OV1 is for example stored in a permanent memory of the comparison module 11.

[64] In the example described here, the first safety threshold OV1 is between

1.10 and 1.25 times the nominal voltage, for example 1.2 times the nominal voltage of the DC voltage source corresponding for example to that of the vehicle on-board network. In this case, in this example, the safety threshold OV1 is 56 volts, i.e. approximately 1.17 times the nominal voltage of the DC voltage source of 48 volts.

[65] The comparison module 11 is further arranged to compare the voltage V measured with a second safety threshold OV2 greater than the first safety threshold OV1. The second safety threshold OV2 is for example stored in a permanent memory of the comparison module 11.

[66] The control system 1 also comprises a control module 12.

In the example described here, the control module 12 is produced from logic gates. Alternatively, the control module 12 can be a

microcontroller.

[67] The comparison module 11 is arranged to transmit to the control module 12 information ov1 when the measured voltage V is greater at the first safety threshold 0V1. This information ov1 is for example transmitted in the form of a high logic level when the measured voltage V is greater than the first safety threshold OV1, and of a low logic level otherwise.

[68] The comparison module 11 is also arranged to transmit to the control module 12 information ov2 when the measured voltage V is greater than the second safety threshold OV2. This information ov2 is for example transmitted in the form of a high logic level when the measured voltage V is greater than the second safety threshold OV2, and of a low logic level otherwise. In the example described here, the second safety threshold is equal to 64 volts or 33% higher than the nominal voltage 48V.

[69] On receipt of the ov1 information, the control module 12 issues a command to close a first group of switches LS, HS, chosen from the group of high side switches HS, that is to say the high group or the low side switch group LS, i.e. the low group.

[70] In the example described here, the first group of switches is the low group LS and the command is an ASC_LS command to close all the switches of the low group LS.

[71] Optionally, on receipt of the ov1 information, the

command 12 can also issue a command to open a second group of switches LS, HS, chosen from the group of high side switches HS, that is to say the high group or the group of low side switches LS, i.e. the low group, the second switch group being different from the first group. In this case, the switching operations of each of the arms X, Y and Z are subject to a dead time during which the upper and lower switches of the arm are both open. The objective is in particular that the switch whose opening is controlled is indeed open before ordering the closing of the other switch in order to ensure that there is no “cross-conduction” according to the expression in English known to those skilled in the art, meaning that the high and low switches are simultaneously closed. [72] In the example described here, the second group of switches is the high group HS and the control module 12 can also issue an opening command for all the switches of the high group HS.

[73] On receipt of the ov2 information, the control module 12 issues a command to close the second group of switches. In this case, in the example described here, the switches of the second group are therefore the switches of the high HS group and the command is an ASC_HS command to close all the switches of the high HS group.

[74] Optionally, on receipt of the ov2 information, the

command 12 can also issue an command to open the first group of switches. In this case, in the example described here, the

switches of the first group are therefore the switches of the low group LS and the command is a command to open all the switches of the low group LS. In this optional case, the commutations of each of the arms X, Y and Z are subject to a dead time.

[75] Thus, in the example described here, in the event of an overvoltage, the

control module 12 first transmits a command to close all the low side switches (low group LS) and optionally a command to open all the high side switches (high group HS).

[76] In [Fig 1], the switches of the low group LS are closed and the

HS high group switches are open. Thus, we can see in [Fig 1], that all the phases U, V, W, are set to the same potential, in this case the potential of the mass of vehicle B-. Thus, the SE electrical system is protected if the fault came from a faulty high side switch that remained open "status fault remained open" or if the fault came from a faulty low side switch that remained closed "status fault remained closed », Or if the fault came from other equipment on the on-board network, such as an untimely disconnection of the first continuous power source B while the rotating electric machine is in generator mode.

[77] If the measured voltage V stabilizes without exceeding the second threshold OV2, the converter is then in a satisfactory state, that is to say in a state in which the overvoltage has been controlled and in which the converter is protected consequences of the overvoltage. In other words, the control system 1 applied the correct strategy for short-circuiting the switching arms of the voltage converter O having regard to the type of fault which caused the overvoltage.

[78] It should be noted that the second threshold must be configured to be

sufficiently far from the first threshold in order to allow the overvoltage time to stabilize below the second threshold when the short-circuiting of the switches of the first group is the correct strategy to be implemented with respect to the type of fault which has generated the overvoltage.

[79] Otherwise, if the control system 1 has not applied the

correct strategy for short-circuiting the switching arms of the voltage converter O, the measured voltage V continues to increase until it exceeds the second threshold OV2. When the second threshold OV2 is exceeded, the control module 12 then transmits a second command to close all the high side switches (high group HS) and possibly a second command to open all the low side switches (low group LS).

[80] At this stage, the control system 1 necessarily applied the

correct strategy for short-circuiting the switching arms of the voltage converter O. Thus, the overvoltage is controlled and the converter is protected from the consequences of this overvoltage.

[81] Optionally, the control module 12 can also

include one or more AE inputs arranged to receive

error information, for example, error information relating to too low a voltage on the on-board network (in English Under Voltage or UV). On receipt of error information on the AE input (s), the control module 12 also issues a command to close the first group of switches and optionally a command to open the second group of switches.

[82] In the embodiment described here, the control unit U further comprises a machine control module 2, a logic module 3 and a controller 4 better known by the English name "driver". [83] The machine control module 2 includes an input (not shown) for receiving an instruction from an electronic vehicle control unit to either put the rotary electric machine in motor mode according to a value of torque supplied, or put the machine electric rotating in alternator mode according to a resistive torque to recharge the DC voltage source of the vehicle. The machine control module 2 transforms this instruction into a command of the high side HS and low side LS switches, said

command being transmitted via logic module 3 and controller 4.

In other words, thanks to the machine control module 2, the logic module 3 and the controller 4, the high side switches HS and the low side switches LS each receive a command, for example by pulse width modulation PWM_HS, PWM_LS, opening or closing.

[84] The logic module 3 is designed to prioritize the commands issued by the control system 1 over the commands issued by the machine control module 2. In other words, the control system 1 has priority over the machine control module 2 .

[85] The logic module 3 therefore receives the command either from the machine control module 2 or from the control system 1 to supply it to the controller 4.

[86] The logic module 3 therefore prioritizes the sending of the command received from the control module 12 over the commands received from the machine control module 2. In other words, when the logic module 3 receives a

command from the control module 12, it transmits this to the controller 4 and at the same time does not transmit to the controller 4 the commands received from the machine control module 2.

[87] When the machine control module 2 is a microprocessor and when the control module 12 and the logic module 3 are produced using logic gates, the reaction time of the machine control module 2 (typically of the order of ten microseconds) is longer than the reaction time of the control module 12 (typically of the order of a microsecond). Thus, the prioritization carried out by the logic module 3 makes it possible to ensure a faster safety setting of the voltage converter O and of the rotating electric machine M. [88] The logic module 3 can also send information ASC_LS_ON, ASC_HS_ON, for example in the form of a logic level, to the machine control module 2 to inform this machine control module 2 that the control module 12 to control the closing of the first group or second group switches.

[89] In this embodiment of the invention, the machine control module 2 can also be connected to the measurement module 11. Thus, in this case, the measurement module 11 can transmit the information ov1 or ov2 to the module machine control 2 which can thus:

1. check that the closing of the switches of the first group or of the

second group by the control module 12 is not an error, and / or

2. transmit to logic module 3 the command to close the

switches of the first group then, if necessary, the command to close the switches of the second group.

[90] Thus, the double transmission of the command to close the switches of the first group and if necessary of the second group makes it possible to have control redundancy and to ensure a higher level of security for the voltage converter 1, in particularly in the case where the control module 12 is faulty.

[91] The machine control module 2 can also optionally include an EV input for measuring the voltage of the voltage source, which in this example is the voltage V measured by the measurement module 10. Thus, the machine control module 2 is able to check the operation of the measurement module 10. In addition, this allows the machine control module 2 to be able to restart in a normal mode when the measured voltage V decreases, for example when the motor control module 2 also receives a informing the vehicle's electronic control unit that the overvoltage came from equipment other than the voltage converter O.

[92] The machine control module 2 can also optionally include an output VS connected to the comparison module 11 to force the comparison module 11 to indicate to the control module 12 that the measured voltage is greater than the first threshold or the second safety threshold in order to verify that the control system 1 is operational.

[93] The machine control module 2 can optionally further comprise other fault or safety detection modules for detecting or anticipating an overvoltage. For example, the machine control module 2 can comprise a phase current direction fault module 9. The fault module 9 is connected to a sensor 90 which measures the direction of the phase current. This could lead to an overvoltage in the event of a wrong phase current direction. Thus, when the machine control module 2 receives information from this safety module 9, the machine control module 2 directly controls the closing of the switches of the first group and optionally the opening of the

switches of the second group.

[94] We will now describe with reference to [Fig 3] the evolution of the

voltage V measured at terminals B + and B- in the event that an inadvertent disconnection of the first continuous power source B occurs.

[95] On the histogram, during a period A called "Normal", the voltage converter O controls the switches on the high side and on the low side

normally according to the instructions of the electronic control unit of the vehicle. During this period A, the measured voltage V is lower than the first safety threshold OV1, in particular for a first duration it is equal to the nominal voltage of the DC voltage source, in this case 48 Volts.

During this period A, at an instant T1, the first continuous power source B disconnects from the on-board network while the rotating electrical machine is in generator mode. This disconnection creates a load shedding phenomenon (in English "load dump") which causes an overvoltage on the on-board network.

[96] Following this disconnection, at an instant T2, the measured voltage V exceeds the first safety threshold OV1, in this case 56 Volts.

[97] The comparison module 11 of the control system 1 then sends to the control module 12 the information ov1 according to which the measured voltage V is greater than the first safety threshold OV1. On receipt of this command, the control module 12 commands the closing of the first group switches and opening of the second group switches. In this case, in this example, the control module 12 sends to the logic module 3 an ASC_LS command to close the low side switches in order to ground the phases and a command to open the high side switches. The logic module 3 retransmits, whatever the commands sent elsewhere by the machine control module 2, these commands to the controller 4 to control the closing of the switches of the low group LS, and the opening of the switches of the high group HS.

[98] We can see on the histogram of [Fig 3] that the measured voltage V

continues to rise up to an instant T3 then stabilizes at a voltage value between the first safety threshold OV1 and the second safety threshold OV2.

[99] This stabilization shows that the control system 1 applied the

correct strategy for short-circuiting the switching arms of the voltage converter O having regard to the type of fault which caused the overvoltage.

[100] We will now describe with reference to [Fig 4] the evolution of the

voltage V measured at terminals B + and B- if a switch on the low side of the voltage converter O remains open.

[101] On the histogram, during a period A called "Normal", the voltage converter O controls the switches on the high side and on the low side

During this period A, at an instant T1, one of the low side switches of the voltage converter O hangs in an open state.

[102] Following this fault appearing on this low side switch, at an instant T2, the measured voltage V exceeds the first safety threshold OV1 in

the occurrence of 56 Volts.

[103] The comparison module 11 of the control system 1 then sends to the control module 12 the information ov1 according to which the measured voltage V is greater than the first safety threshold 0V1. On receipt of this command, the control module 12 commands the closing of the

first group switches and opening of the second group switches. In this case, in this example, the control module 12 sends the logic module 3 an ASC_LS command to close the low side switches in order to ground the phases and a command to open the high side switches. The logic module 3 retransmits, whatever the commands emitted by the machine control module 2, these commands to the controller 4 to control the closing of the switches of the low group LS, and the opening of the switches of the high group HS.

[104] We can see on the histogram of [Fig 4] that the measured voltage V does not stabilize and continues to increase until it reaches and then exceeds a voltage value greater than the second safety threshold OV2.

[105] This continuous rise in the measured voltage V shows that the control system 1 has not applied the correct strategy for short-circuiting the switching arms of the voltage converter O having regard to the type of fault causing the overvoltage. .

[106] In fact, the faulty low-side transistor remained open and at least one phase of the rotating electrical machine was not short-circuited to ground.

[107] The measured voltage V exceeding the second safety threshold OV2 in

the occurrence of 64 Volts, the comparison module 11 of the

command 1 then sends to the control module 12 the information ov2 according to which the measured voltage V is greater than the second safety threshold OV2. On receipt of this command, the control module 12 controls the closing of the switches of the second group and the opening of the switches of the first group. In this case, in this example, the control module 12 sends to the logic module 3 an ASC_HS command to close the high side switches and a command to open the low side switches. The logic module 3 retransmits, whatever the commands emitted by the machine control module 2, these commands to the controller 4 to control the opening of the switches of the low group LS, and the closing of the switches of the high group HS.

[108] We can see on the histogram of [Fig 4] that the measured voltage V

continues to rise until moment T3 and stabilizes at a voltage value higher than the second safety threshold OV2.

[109] This stabilization shows that the control system 1 applied the

correct strategy for short-circuiting the switching arms of the

voltage converter O having regard to the type of fault which caused the overvoltage.

[110] The previously described embodiment may not include one or more of the functionalities described above as optional.

[111] Naturally, the invention is not limited to the embodiments described with reference to the figures and variants could be envisaged without departing from the scope of the invention.

[112] Thus in the embodiment described above, the switches of the first group are the low side switches and the switches of the second group the high side switches but in a variant, the

switches of the first group can be the high side switches and the switches of the second group the low side switches.

[113] Likewise, the rotary machine described above is a machine

three phase. As a variant, the electric rotary machine can more generally have n phases, for example n = 6 for a hexaphase machine. In this case, the voltage converter O also has n switching arms.

[114] Similarly, in the embodiment described above, the coils u, v, w are mounted in a star. Alternatively, the coils u, v, w can be mounted in a triangle.

[115] Likewise, in the embodiment described above, the module

logic 3, the control module 12 and the machine control module 2 are produced in the form of separate entities. As a variant, the logic module 3, the control module 12 and the machine control module 2 can be produced in the form of a single entity, for example a microcontroller comprising a programmable logic circuit, for example of the FPGA type (from the English “Field-Programmable Gate Array”)

[116] In addition, in the embodiment described above, the high side and low side transistors are MOSFETs. As a variant, these transistors can be IGBTs.

Claims

[Claim 1] [Control system (1) of a voltage converter (O), the voltage converter (O) being intended to connect a rotary electrical machine (M) to a direct voltage source (B), in particular to an on-board network, the voltage converter (O) comprising a plurality of switching arms (X, Y, Z) connected in parallel, each arm (X, Y, Z) comprising a high-side switch (HS_X, HS_Y , HS_Z) and a low side switch (LS_X, LS_Y, LS_Z) connected to each other at a midpoint (PX, PY, PZ) intended to be connected to said rotary electrical machine, the high side switches forming a high group (HS) and the low side switches forming a low group (LS), the control system (1) comprising:

at. a module (10) for measuring the voltage (V) of the direct voltage source (B),

b. a comparison module (11) of the measured voltage (V) to a

first safety threshold (OV1),

vs. a control module (12) for generating a control command

closing of a first group of switches (LS) chosen from the high group (HS) or the low group (LS), if the comparison module (11) indicates that the measured voltage (V) is greater than the first threshold security (OV1).

[Claim 2] Control system (1) according to claim 1, in which the measured voltage (V) is the voltage between two terminals (B +, B-) of the voltage converter (O) intended to be connected to the source of DC voltage (B).

[Claim 3] Control system (1) according to claim 1 or 2, wherein, when the measured voltage (V) is greater than or equal to the first safety threshold (OV1), the control module (12) is further designed to generate a command to open switches other than those of the first group.

[Claim 4] Control system (1) according to one of

Claims 1 to 3, in which the comparison module (11) compares the measured voltage (V) at a second safety threshold (OV2) greater than the first safety threshold (OV1) and in that the control module (12) is further designed for, when the measured voltage (V) is higher or equal to the second safety threshold (OV2), generate a command to close a second group of switches chosen from the high group (HS) or the low group (LS), said second group of switches being different from said first group switch.

[Claim 5] Control system (1) according to claim 5, in which the control module (12) is further designed to generate a command to open the first switch group when the measured voltage (V) is greater or equal to the second safety threshold (OV2).

[Claim 6] Control system (1) according to one of

previous claims wherein the first group of switches (LS) is the bottom group (LS).

[Claim 7] Electrical system (SE) comprising:

at. first and second supply terminals (B +, B-) intended to be connected to a direct voltage source (B), in particular to a battery of a motor vehicle,

b. a rotary electrical machine (M) comprising a stator having at least three phases (U, V, W),

vs. a voltage converter (O) for supplying the rotary electrical machine (M) from said direct voltage source (B), the voltage converter (O) comprising:

i. a plurality of switching arms (X, Y, Z) mounted in

parallel, each arm (X, Y, Z) comprising a high side switch (HS_X, HS_Y, HS_Z) and a low side switch (LS_X, LS_Y, LS_Z) connected to each other at a midpoint ( PX, PY, PZ), each midpoint (PX, PY, PZ) being connected to at least one phase (U, V, W) of said rotary electrical machine (M), and

ii. a control unit (U) for the high side and low side switches, said control unit (U) comprising a control system (1) according to one of the preceding claims.

[Claim 8] Electrical system (SE), in which the unit of

control (U) further comprises at least one fault detection module (9), for example a phase current sense fault module, and in which when the fault module (9) detects a fault, l the control unit (U) controls the first group of switches when closing.

[Claim 9] Electrical system (SE) according to claim 7 or 8, wherein the control unit (U) further comprises:

at. - a controller (4) designed to control the high side and low side switches,

b. a machine control module (2) intended to receive an instruction from an electronic vehicle control unit to either put the rotary electric machine (M) in engine mode, or put the rotary electric machine (M) in alternator mode, and arranged to transform this instruction into a command for controlling the high side (HS) and low side (LS) switches of the

voltage converter (O),

vs. a logic module (3) to prioritize the commands issued by the

control system (1) relative to the commands issued by the machine control module (2), the logic module (3) transmitting to the controller (4) the command of the switches received either by the machine control module (2) or by the control system (1).

[Claim 10] Method for controlling a control system of a voltage converter according to one of claims 1 to 6, the voltage converter (O) being connected to a rotary electrical machine (M) and to a source of direct voltage (B), in particular to an on-board network, said method comprising:

at. A step of measurement by the measurement module (10) of the voltage (V) of the DC voltage source (B),

b. A step of comparison by the comparison module (11) of the measured voltage (V) to a first safety threshold (OV1),

vs. A step of generation by the control module (12) of a

command to close a first group of switches (LS) chosen from the high group (HS) or the low group (LS), if the measured voltage (V) is greater than the first safety threshold (OV1).]